Drug use in Argentina has consistently played a significant role in the country's HIV/AIDS epidemic;it has one of the highest rates of drug use-related HIV prevalence in Latin America. After witnessing the ineffectiveness of the government's prohibitionist and abstinence-based policies and interventions in curbing disease transmission, various non-governmental organizations (NGOs) in Argentina begun adopting harm reduction as an alternate means of addressing the health of drug users. Originating in Europe, Australia, and North America in the 1980s, harm reduction is best described as a public health approach that places priority on reducing the negative consequences of drug use in a gradual manner rather than focusing on eliminating drug use altogether. Unlike NGOs, however, the Argentine government has only marginally utilized this model in their projects. This dissertation research examines drug use and the employment of the harm reduction model in Buenos Aires and Rosario, Argentina, since the mid-1990s. By focusing on the practices of Argentine NGOs, this research ethnographically examines how the adoption of this public health model and the philosophy that accompanies it have affected both institutional approaches to drug use and users as well as the everyday practices of drug use in Argentina's largest urban centers. Specifically, it is hypothesized that local NGOs that utilize the harm reduction model are modifying how drug use, drug users, and drug user health - including but not only HIV/AIDS - are discussed, understood, and managed in the Argentine context. Research was multi-faceted and focused on the collection of qualitative data. Extensive fieldwork was conducted in the metropolitan areas of Buenos Aires and Rosario, Argentina, from September 2007 to October 2008. First, in-depth archival research included an analysis of the existing literature on drug use, addiction, and public health interventions in Argentina. Second, ethnographic fieldwork was carried out using participant observation and open-ended, semi-structured interviews with members of NGOs, public health professionals, and drug users. Third, one-time, structured interviews were conducted with government personnel that work in the fields of drug use and addiction. This in-depth ethnographic analysis of harm reduction in Argentina is relevant to public health in the United States because it (a) explores how a specific public health model is utilized on a local level;(b) examines the impact of civil society in implementing patient-centered health interventions among drug users;and (c) analyzes the possibilities of reproducing the Argentine NGOs'model of care in the United States.